One type of firing mechanism commonly used in semiautomatic handguns includes a hammer which is pivotable from a rearward cocked position to a forward position for impacting the firing pin. A sear releasably retains the hammer in its cocked position with the hammer spring or main spring in compression. When the trigger is actuated, the sear is moved to release the hammer that is moved by the stored energy of the main spring, to strike the firing pin which is thereby driven forward to fire a chambered round. The principal drawback of this type of mechanism is that it includes numerous parts and is relatively complex and expensive to manufacture.
Another common configuration is disclosed in U.S. Pat. No. 3,857,325 to Thomas, which is hereby incorporated by reference in its entirety, wherein a striker-type firing pin is utilized in lieu of a pivotable hammer. In past embodiments of this mechanism, the firing pin was actuated by an action of a trigger bar engaged to a trigger which moved the firing pin axially along the length of the bore of the barrel causing the sear to rotate about its pivot point. As the sear rotated, a spring was compressed as the sear block cam engaging member engaged a cam surface on the sear. This caused the upper sear portion to be displaced downward relative to the firing pin. Therefore, during the movement of the trigger backwards, the rearward movement of the firing pin corresponded with a downward movement of the upper sear element gradually lessening the amount of surface of the sear abutment in contact with the firing pin leg until the firing pin leg was free of the sear and the firing pin moved forward urged on by the spring and strike the rear of the casing and discharge the round. This embodiment of sear block was characterized by two elements, the sear and a pivot arm, which were moveable relative to one another along an axis as depicted in U.S. Pat. No. 5,386,659, which is hereby incorporated by reference in its entirety. There was also a spring urging the upper element to remain at its fully displaced position.
Consequently, this required, in certain embodiments, a land in the sear block casing which would have prevented the upper sear element from moving along an axis perpendicular to the bore axis, and hence, eliminate the overlap and contact area of the abutment with the leg of the firing pin, such that only when the sear was rotated almost its full extent, was it capable of being displaced along the perpendicular sear axis. In addition, there is a requirement of a second surface formed in the sear block housing which caused an element to cam along its surface creating a force to oppose that of the sear block spring and thereby urging the upper seal element downward along the perpendicular axis and reducing the overlap between the abutment and the leg of the firing pin.
In later embodiments, the inner land which prevents the movement of the upper sear element along the perpendicular axis was eliminated and the sear spring was increased in force to ensure retention of the firing pin.
The present invention provides a simplified sear assembly that is less expensive to manufacture as the number of components and surfaces are reduced. Additionally, the present invention provides an improved trigger pull and trigger movement over the prior art.